1. Field of the Invention
This invention relates to the automatic control of the idling on autovehicles with controlled ignition.
2. Description of the Prior Art.
The objective in controlling idling speed is to keep an idling speed as near as possible to the instruction value and to return idling speed to the instruction value quickly without pumping when it deviates suddenly under the influence of an outside disturbance (variations of richness, advance, letting up on the accelerator, pulling of the power steering, etc.).
For that purpose, the quantity of air admitted into the intake manifold is affected by using an actuator that operates, either by causing the section of a bypass to vary, or by more or less half opening the butterfly, the standard idling stop then being made mobile.
At idling, engines are often the site of intrinsic pumping phenomena (gaps in richness due to the oxygen probe, ignition jumps, richness-filling resonance, etc.). It does not pertain to the control of the idling speed to eliminate them, that is the job of the engine mechanics. On the other hand, the process of governing the control must be careful not to amplify them, while strictly correcting any deviation of speed in relation to the instruction.
These processes are already known, but these prior processes exhibit the following drawbacks:
Either they work with speed and the latter is expensive to obtain in time and in loading of memory, or they work with periods, and nothing intrinsic in the basic algorithm filters the insignificant variations from one cycle to the other.
They do not offer, as does this invention, the possibility of passing, almost without modifications, from one type of actuator to another (double-pole continuous motor to a stepping motor).
The time of a corrective command of the actuator can exceed the period separating two consecutive ignitions. A complex management of times results for the microprocessor and the integration with an injection-ignition process is difficult under these conditions.
In the absence of integral effect, on the one hand, the accuracy on the final value attained is poor and, on the other hand, an unfortunate propensity for amplifying the instabilities of the engine is noted.
The output to the actuator is complex, therefore hard to manage. For example, it comes down to the proportional effect of deciding or not on a corrective pulse while the differential effect receives the role of controlling the amplitude.
Their basic strategy does not implicitly have an anti-overshoot effect during the returns to the instruction value on letting up on the accelerator.